Disks are recorded at either constant angular velocity (CAV) or constant linear velocity (CLV). FIG. 5 is an illustrative view for explaining the track pattern of the disk recorded in the CAV mode. In general, the track is divided into certain blocks referred to as a sector having a data area and an address mark area indicating a position which the data area is located on the disk. FIG. 5 shows eight sectors divided at equal angles. The hard address mark area 24 which separates the track into individual sectors is preformed when pressing the disk. The preformed hard address mark area 24 is arranged on a radial straight line of the disk so as to avoid cross talk from the address mark area to the data area. This cross talk has important effects on reconstruction of the data.
The disadvantage of CAV recording is that the storage capacity of the entire disk decreases because of the increase in tangential velocity at the outside radius than that of the inside radius and the resultant unnecessary increase in pit length at the outside radius.
On the other hand, since CLV recordings provide higher packing density in comparison to CAV recordings because of its constant linear velocity, it follows that the storage capacity increases. FIG. 6 is a schematic drawing for illustrating the track pattern of the disk recorded in the CLV mode. If the track is divided by the sectors having the same length, it becomes the layout that the address mark areas 25 are located in close proximity to the data areas 26 in the adjacent track as shown in FIG. 6. Because the information data recorded on the disk is picked out via that the optical head detects the microscopic optical variation in the incoming light beam from the disk surface, large cross talk from the hard address mark area in the adjacent track results in the increase in an error rate of the reproduced data. Consequently, the hard address mark areas, such as those preformed in the disk pressing which described in the CAV recording disk shown in FIG. 5, can not be used because there is the large cross talk from the hard address mark to the weak data area in the adjacent track.